Revert "Force CtsNetTestCases to compile with Kotlin 1.9"

With b/391766151 fixed by the previous patch, this can now
be reverted.

This reverts commit 4f59de2f85afbeb938646955b44be875e74d07b1.

Test: atest NetworkAgentTest on an S device
Change-Id: Ie2cb2ca5653a134c0eaa1cac5b0c4b4221f1c0ac
1 file changed